diff --git a/internal/protocol/protocol.go b/internal/protocol/protocol.go
index e65d5e72..a5525679 100644
--- a/internal/protocol/protocol.go
+++ b/internal/protocol/protocol.go
@@ -356,6 +356,11 @@ func (c *rawConnection) readMessage() (hdr header, msg encodable, err error) {
 		l.Debugf("read header %v (msglen=%d)", hdr, msglen)
 	}
 
+	if hdr.version != 0 {
+		err = fmt.Errorf("unknown protocol version 0x%x", hdr.version)
+		return
+	}
+
 	if cap(c.rdbuf0) < msglen {
 		c.rdbuf0 = make([]byte, msglen)
 	} else {
diff --git a/internal/protocol/protocol_test.go b/internal/protocol/protocol_test.go
index 9da9422c..75e0086e 100644
--- a/internal/protocol/protocol_test.go
+++ b/internal/protocol/protocol_test.go
@@ -189,7 +189,7 @@ func TestVersionErr(t *testing.T) {
 		msgID:   0,
 		msgType: 0,
 	}))
-	w.WriteUint32(0)
+	w.WriteUint32(0) // Avoids reader closing due to EOF
 
 	if !m1.isClosed() {
 		t.Error("Connection should close due to unknown version")
@@ -212,7 +212,7 @@ func TestTypeErr(t *testing.T) {
 		msgID:   0,
 		msgType: 42,
 	}))
-	w.WriteUint32(0)
+	w.WriteUint32(0) // Avoids reader closing due to EOF
 
 	if !m1.isClosed() {
 		t.Error("Connection should close due to unknown message type")